Energy Efficiency and Economic Viability as Decision Factors in the Rehabilitation of Historic Buildings

The restoration of historical buildings often implies a change in the main use of the building so that it can once again become a part of people’s lives. Among the interventions needed to adapt the buildings to their new purpose, improving the energy performance is always a challenge due to their particular construction solutions and the influence that these improvements can have on their protected elements. The regulations in force in European Union (EU) member states leave a gap in how the energy performance evaluations in these types of buildings can be defined, and even exclude them from the process. However, rehabilitation of buildings is always seen as an opportunity, because it allows the building to once again be useful to society and play an important role in people’s lives. At the same time, it can also improve their performance and allow benefits to be gained from their use through a reduction in maintenance costs. In the rehabilitation process, the economic viability of the renovation plays a fundamental role which must be compared, in the case of protected buildings, to its impact on the architecture of the building. Since 2002, the EU has issued directives with the aim that countries should define objective methods to improve the energy performance of buildings and, in recent times, methods that demonstrate the amortization of such improvements. Within the process of implementing the new methodologies adapted to the EPBD, Spain was one of the last EU countries to define a process for the energy assessment of existing buildings, introducing an analysis of the economic viability of the construction improvements suggested in the process. The objective of this research was to describe the decision-making process during the evaluation of the feasibility of introducing construction improvements to the energy performance of two catalogued historic buildings located in a warm climate. The estimated energy consumption was evaluated, the net present value (NPV) and the payback period of the investment calculated, and the results obtained were compared with the real energy consumption. At the end of the process, it can be said that the methodologies adopted in Spain offer results that can lead designers to make wrong decisions that may affect the protected heritage values of these buildings.